Abstract
Thermomechanical properties and crystallization behavior of poly(ethylene terephthalate) (PET) nanocomposites containing layered double hydroxide (LDH) were investigated. To enhance the compatibility between PET matrix and LDH, dimethyl 5โsulfoisophthalate (DMSI) anion intercalated LDH (LDHโDMSI) was synthesized by coprecipitation method, and its structure was confirmed by Fourier transform infrared (FTIR) spectrometer and Xโray diffraction (XRD) measurements. Then, PET nanocomposites with LDHโDMSI content of 0, 0.5, 1.0, and 2.0 wt% were prepared by inโsitu polymerization. The dispersion morphologies were observed by transmission electron microscopy (TEM) and XRD, showing that LDHโDMSI was exfoliated in PET matrix. Thermal and mechanical properties, such as thermal stability, tensile modulus, and tensile yield strength of nanocomposites, were enhanced by exfoliated LDHโDMSI nanolayers. However, elongation at break was drastically decreased with LDH loading owing to the increased stiffness and microvoids. The effect of exfoliated nanolayers, which acted as a nucleating agent confirmed by differential scanning calorimeter (DSC), on the microstructural parameters during isothermal crystallization, was analyzed by synchrotron smallโangle Xโray scattering (SAXS). It is believed that nanocomposites could be crystallized more easily owing to the increased nucleation sites, which lead to the decrease of average amorphous region size and the long period with the increase of LDHโDMSI content. ยฉ 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 28โ40, 2007